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THE ICES WORKING GROUP ON OCEANIC HYDROGRAPHY:
BUILDING ON OVER 100 YEARS OF NORTH ATLANTIC OBSERVATIONS
N.P. Holliday(1), H. Valdimarsson(2), G. Nolan(3), S.L. Hughe (4),
A. Lavín 5), S. Østerhus(6), T. Sherwin(7), A. Trofimov(8)
(1)
National Oceanography Centre, Southampton, Waterfront Campus, European Way, Southampton SO14 3ZH,
United Kingdom, Email: [email protected]
(2)
Marine Research Institute, PO Box 1390, Skulagata 2, 121 Reykjavic, Iceland, Email: [email protected]
(3)
Marine Institute, Rinville, Oranmore, Co. Galway, Ireland, Email: [email protected]
(4)
Marine Scotland, Marine Laboratory, PO Box 101, 375 Victoria Road, Aberdeen, AB11 9DB, Scotland,
United Kingdom, Email: [email protected]
(5)
Instituto Español de Oceanografía, Apdo 240, 39080 Santander, Spain, Email: [email protected]
(6)
Bjerknes Centre for Climate Research, Allégaten 55, NO-5007 Bergen, Norway,
Email: [email protected]
(7)
Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, Oban, Argyll, PA37 1QA, Scotland,
United Kingdom, Email: [email protected]
(8)
Knipovich Polar Research Institute of Marine Fisheries and Oceanography (PINRO), 6 Knipovich Street, Murmansk
183038, Russia, Email: [email protected]
ABSTRACT
The ICES (International Council for the Exploration of
the Sea) Working Group on Oceanic Hydrography
(WGOH) maintains, analyses and develops coastal,
shelf and deep ocean repeated stations and sections
around the subpolar North Atlantic, the Nordic Seas and
adjacent shelf seas. The WGOH annually reviews the
latest results and research from repeat hydrography
sections and stations, and generates a summary of
hydrographic conditions in the North Atlantic, the ICES
Report on Ocean Climate (IROC).
By combining expertise in variability in physical
processes and the relationship with ecosystems from
around the North Atlantic, the WGOH is an excellent
forum for developing new insight into climate
variability and the impact on ecosystems. Recent new
collaborative research highlights include observations of
unusually warm and saline Atlantic Water in the Nordic
Seas, a comparison of gridded sea surface temperature
products to selected time series, and an isopycnal
analysis over 300,000 profiles from the Nordic Seas.
The WGOH encourages development of new time series
and the use of new technology, and has led to the
establishment of new ADCP (Acoustic Doppler Current
Profiler) and surface observations from voluntary
observing ships. Future challenges for WGOH include
maintaining the integrity of time series, and
communicating the information from the time series in a
useful way to a wide range of stakeholders.
The ICES WGOH has no dedicated funding, instead
participants and time series are funded by member
nations which are Canada, Denmark, Estonia, Faroes,
Finland,
France,
Germany,
Iceland,
Ireland,
Netherlands, Norway, Poland, Portugal, Russia, Spain,
Sweden, UK and USA.
1. INTRODUCTION
The International Council for the Exploration of the Sea
(ICES) was established in 1902 to "promote and
encourage research ... for the study of the sea,
particularly the living resources thereof", with a focus
on the North Atlantic and adjacent seas. It is a regional,
intergovernmental organisation, and it provides advice
to governments and other bodies on such matters as
fisheries and pollution. The physics of ocean circulation
and the long-term variability in ocean climate has
always been important to ICES, and takes place within
the ICES Working Group on Oceanic Hydrography
(WGOH). The Group analyses the most recent
observations of the deep ocean and adjacent deep and
shallow basins: the North Atlantic and Nordic
(Greenland, Iceland and Norwegian) Seas, and the
Labrador, Barents, Baltic and North Seas. Typically
data are presented that are only months or even weeks
old, making this an excellent forum for understanding
the present physical state of the ocean. Each new data
set is presented in the context of long-term observations;
some records go back 100 years. With data spread
across the region, the WGOH is also in a good position
to understand the basin-scale processes that link
individual time series. A WGOH collaborative paper [1]
showed that recent unusually warm and saline North
Atlantic water from the subpolar gyre could be traced
through the Nordic Seas to the Fram Strait where it
enters the Arctic ocean.
The members of the WGOH are research and fisheries
scientists dedicated to making high quality
measurements and using them to understand how the
ocean works. Current research being undertaken by
members covers a wide range of topics from surface
processes to deep overflows, across the North Atlantic
from the western deep ocean basins to the wide eastern
shelf seas, and from the subtropical gyre to the Arctic
[2-14]. The focus is on interannual to decadal
variability, including the mechanisms that determine
properties and transports [1], [12-20]. A particular
feature of research within the WGOH is the links
between physical conditions and biological systems [2126]. The use of new technology is a further strength of
research within the WGOH [27] and[ 28].
were able to analyse over 300,000 temperature and
salinity profiles for the 1951-2000 period (Fig. 2 [29]).
The analysis of data on isopycnal surfaces showed
property variations that are significantly different to
those on a depth surface.
A further resource are data collected by voluntary
observing ships which measure temperature and salinity
with XBTs and thermosalinographs, and ocean currents
with ADCPs. The results from monthly sampling of
surface and bottom temperatures for nearly three
decades in the Mid Atlantic Bight reveal the power of
systematic or repeat sampling from merchant marine
vessels.
2. THE OBSERVING NETWORK
The observing network that is analysed and maintained
by the WGOH is characterised by numerous short
hydrographic sections, time series stations and a small
number of basin-scale coast-to-coast sections (Fig. 1).
The sections and stations are typically sampled from 1
to 4 times per year, though some stations are sampled as
much as daily or weekly. Many have chemical and
biological observations associated with them and are
analysed in an ecosystem context. The WGOH includes
time series that are over 100 years long; for example,
the Faroe-Shetland Channel sections began in 1893, and
the Kola section in the Barents Sea began in 1900. The
most frequently-occupied, long, deep ocean time series
is at Ocean Weather Station "M" in the Norwegian Sea,
which started in 1948.
The WGOH actively encourages the development of the
observing network, including the establishment and
reporting of new time series. One example is a new
group of repeated hydrographic sections run by Ireland
on the NW European continental shelf, which were
developed in consultation with the WGOH. Another
recent example is the instrumenting of a Faroese ferry,
MV Norrona, with a thermosalinograph and ADCP, in
order to collect data along its routes across the North
Sea and the deep North Atlantic. The WGOH also
supports the revival of long time series, which have
suffered a hiatus in data collection through a lack of
funding. For example a recent new member will bring
data from a time series station in the English Channel to
the forum; the series was begun in 1903, but has a gap
from 1985-2002 when funding was withdrawn. By
including the new member and time series, the WGOH
will aid the analysis of the recent station data, and
improve regional understanding by synthesising all
available data.
3. COMMUNICATING INFORMATION
Figure 1. The repeat hydrography sections
and stations of the ICES WGOH.
In addition to the illustrated sections, the WGOH
utilises opportunistic data from academic research
cruises and fisheries surveys to understand variability
and physical processes. These additional data are a
crucial, varying resource, which cannot easily be shown
on a schematic map. For example, by combining Nordic
Seas data from the ICES data centre and PINRO
(Murmansk-based Polar Scientific Institute for Fishery
and Oceanography) in Murmansk, Russia, the WGOH
Each year the WGOH generates a co-operative research
report that summarises the physical conditions in the
North Atlantic and Nordic Seas. The ICES Report on
Ocean Climate (IROC) describes the status of sea
temperature and salinity during the previous year, as
well as observed trends over the last decade or longer.
Information from the longest time series provides an
overview of temperature and salinity changes in the
ICES area (Fig. 3). The IROC can be found at
www.ices.dk/marineworld/oceanclimate.asp.
Horizontal fields of North Atlantic ocean temperature
and salinity at various depths (10m, 300m, 1000m), and
mixed layer depths are provided for recent years. The
maps are generated from in situ data (including Argo
float temperature and salinity profiles) and satellite data.
These products are extremely useful for placing the
scattered time series into regional context, as well as
providing new views of interannual variability.
The main body of the IROC consists of detailed
descriptions and figures describing the individual time
series (Fig. 4). Data are sometimes presented as
anomalies from monthly or seasonal means, since the
seasonal cycle has a much higher amplitude than the
interannual variability. Where data resolution permits,
Figure 2. Hydrographic data from ICES data centre and PINRO, Russia,
for the period 1950-2000 grouped according to season [29].
the most recent observations are plotted against longterm monthly means.
Recent developments in the content of the IROC include
improving the information about the deep ocean. The
main focus of the IROC has been the upper ocean, but
significant changes occur at intermediate and deep
levels too, and these have fundamental influences on
circulation and ecosystems. Many of the time series
sample the abyssal ocean and the WGOH is
consolidating these data to provide an overview of
recent conditions at depth.
WGOH contributed to the production of a climaterelated brochure [31], which is aimed at all ICES
stakeholders, including non-experts. The WGOH also
communicates research results in annual meeting
reports, through presentations at conferences, and
through refereed publications. A recent comparison of
gridded sea surface temperature products with some
WGOH time series should provide guidance to
researchers using the products for their analyses [32].
All WGOH data are archived at national data centres
and in the ICES data centre.
4. FUTURE PLANS AND CHALLENGES
The WGOH communicates data and information to the
ICES stakeholders, policymakers and the broader
research community. There is a wide range of level of
expertise, which the WGOH needs to consider. The
IROC is one route, primarily aimed at scientists with a
range of understanding of physical oceanography. The
1. It is of vital importance that the existing time series
are maintained. For many time series, there is a lack
of funding security; most are maintained through a
rolling programme of grants for a short number of
years. Many time series face funding shortages
periodically, especially during times when the
Figure 3. The IROC North Atlantic upper ocean temperature overview
(Fig. 1 from IROC 2007 [30], see report for full caption).
Figure 4. Norwegian Sea temperature and salinity anomalies, and monthly temperature and salinity
at 50m at Ocean Weather Station "M" (66°N 2°E) (Figs. 57 and 58 from IROC 2007[30])
political climate turns against ocean monitoring.
Some series have suffered major gaps as a result,
and some have reduced temporal resolution in recent
years.
2. It is also vital to maintain the continuity and
integrity of the time series, to ensure that future
observed changes are not artefacts of the
instrumentation or platform used to make the
measurements. The use of remote and autonomous
instruments and vehicles is already increasing
(moored profilers, floats, gliders etc), and it is
anticipated that these methods will enhance shipbased measurements and in places will replace them.
It is essential that a change in technology is brought
in with a sufficient assessment period to avoid
continuity problems.
3. The WGOH is dedicated to improving access to data
and information and there remain some challenges to
resolve. One objective of the IROC is to alert the
research community to the wealth of data and
analysis available. This approach has been
reasonably successful, with the IROC being cited in
an increasing number of reports and published
papers. The WGOH is continually seeking new ways
to promote their data resource and to communicate
their research activities. All WGOH data are
archived in national data centres, and some
proportion, but by no means all, are archived in
international data centres such as ICES and WODC.
The WGOH aims to increase the amount of data
being routinely sent to ICES and WODC, and to
assist the ICES data centre in making their archives
more easily accessible. Finally, few data collected
by WGOH members are transmitted in real-time or
near real-time; the challenge for members is to
increase this activity.
4. The WGOH is a key component within the
ecosystem approach adopted by ICES for fisheries
advice and management. One challenge is to
continue providing information in a form that is
accessible and useful. A further major challenge is to
generate the research that will improve the
understanding of ecosystem variability.
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